Shearing only working on the 2 axis I don't want
By default the Shear tool axis will be the one of the view, for example if the view is this one, the X and Y axis will be these ones:

So if you keep the default Orientation and shear on the X axis, the view will be the axis and the vertices will move along the view's X axis, like this:

But you can also choose to shear on the Global, Local axis, etc... You need to choose the Orientation in the Operator box. In this box, the Axis will be the rotation pivot axis, the Axis Ortho will be the axis along which the vertices move, the Offset will be the amount of units they move.

In your case you can either put your view on top (7) and shear on the Y axis, or stay in user view, press ShiftCtrlAltS to shear, press Enter right away, and in the Operator box, switch the Orientation to Global, Axis &gt; Z, Axis Ortho &gt; Y.